Sustained release compositions, process for producing the same and use thereof

ABSTRACT

Sustained release compositions containing a physiologically active substance or its salt, hydroxynaphthoic acid or its salt and a lactic acid-glycolic polymer or its salt, wherein the product of the weight-average molecular weight of the lactic acid-glycolic acid polymer by the amount (μmol) of the terminal carboxyl group per unit mass (g) of the lactic acid-glycolic acid polymer is from 1,200,000 to 3,000,000 (inclusive); and their production; medicaments containing these sustained release compositions, etc.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of application Ser. No. 10/019,786,filed Jan. 4, 2002, which is a National Stage application ofPCT/JP00/04683, filed Jul. 13, 2000, which claims priority from Japanesepatent application JP 201887/1999, filed Jul. 15, 1999.

FIELD OF THE INVENTION

The present invention relates to a sustained release formulation of apharmacologically active substance and a method for producing the same.

BACKGROUND OF THE INVENTION

JP-A-7-97334 discloses a sustained release formulation consisting of aphysiologically active peptide or its salt and a biodegradable polymerhaving a terminal free carboxyl group as well as a method for producingthe same.

Each of GB2209937, GB2234169, GB2234896, GB2257909 and EP626170A2discloses a composition comprising as a base a biodegradable polymercontaining a water-insoluble salt such as a pamoate of a peptide or aprotein prepared separately as well as a method for producing the same.

WO95/15767 discloses an embonate (pamoate) of cetrorelix (LH-RHantagonist) and a method for producing the same, and describes that thispamoate, even when enclosed in a biodegradable polymer, exhibits thepeptide-releasing performance equivalent to the pamoate which existsindependently.

DISCLOSURE OF THE INVENTION

There is provided a novel composition containing a physiologicallyactive substance at a high concentration whose excessive initial releaseis suppressed whereby accomplishing a stable releasing rate over aprolonged period (preferably about 6 months or longer).

The present inventors made an effort to solve the problems describedabove and finally discovered that by allowing a physiologically activesubstance and a hydroxynaphthoic acid to coexist upon forming acomposition the physiologically active substance can be introduced at ahigh concentration into the composition; that further by enclosing thesetwo components into a lactic acid-glycolic acid polymer thephysiologically active substance can be released at a releasing ratedifferent from the rate at which the physiologically active substance isreleased from a composition formed from the physiologically activesubstance and the hydroxynaphthoic acid prepared in the absence of thelactic acid-glycolic acid polymer; that this releasing rate can becontrolled by selecting the characteristics of the lactic acid-glycolcacid polymer and the amount of the hydroxynaphthoic acid; that aninitial excessive release can surely be suppressed even at a highconcentration whereby accomplishing a sustained release over anextremely prolonged period (preferably about 6 months or longer); andalso that by employing a lactic acid-glycolic acid polymer whose weightaverage molecular weight multiplied by the amount (μmol) of the terminalcarboxyl group per unit mass (g) of the lactic acid-glycolic acidpolymer is 1,200,000 to 3,000,000 (inclusive) a further satisfactorysustained release formulation can be provided. As a result of a furthereffort, the present invention was completed.

Thus, the present invention provides:

(1) a sustained release composition comprising a pharmacologicallyactive substance or its salt, a hydroxynaphthoic acid or its salt and alactic acid-glycolic acid polymer or its salt, wherein the product ofthe weight average molecular weight of said lactic acid-glycolic acidpolymer by the amount (μmol) of the terminal carboxyl group per unitmass (g) of said lactic acid-glycolic acid polymer is 1,200,000 to3,000,000 (inclusive);

(2) the sustained release composition according to the above-mentioned(1), wherein the pharmacologically active substance is a physiologicallyactive peptide;

(3) the sustained release composition according to the above-mentioned(1), wherein the pharmacologically active substance is an LH-RHderivative;

(4) the sustained release composition according to the above-mentioned(1), wherein the hydroxynaphthoic acid is 1-hydroxy-2-naphthoic acid or3-hydroxy-2-naphthoic acid;

(5) the sustained release composition according to the above-mentioned(1), wherein the hydroxynaphthoic acid is 1-hydroxy-2-naphthoic acid.

(6) the sustained release composition according to the above-mentioned(1) wherein the % molar ratio between lactic acid and glycolic acid is100/0 to 40/60;

(7) the sustained release composition according to the above-mentioned(1), wherein the % molar ratio between lactic acid and glycolic acid is100/0;

(8) the sustained release composition according to the above-mentioned(1), wherein the weight average molecular weight of the polymer is about3,000 to about 100,000;

(9) the sustained release composition according to the above-mentioned

(8), wherein the weight average molecular weight is about 20,000 toabout 50,000;

(10) the sustained release composition according to the above-mentioned(3), wherein the LH-RH derivative is a peptide represented by Formula:5-oxo-Pro-His-Trp-Ser-Tyr-Y-Leu-Arg-Pro-Zwherein Y denotes DLeu, DAla, DTrp, DSer(tBu), D2Nal or DHis(ImBzl), andZ denotes NH—C₂H₅ or Gly-NH₂;(11) the sustained release composition according to the above-mentioned(1), wherein the amount (μmol) of the terminal carboxyl group of thepolymer is 50 to 90 μmol per unit mass (g) of the polymer;(12) the sustained release composition according to the above-mentioned(3), wherein the molar ratio between the hydroxynaphthoic acid or itssalt and the LH-RH derivative or its salt is 3:4 to 4:3;(13) the sustained release composition according to the above-mentioned(3) which contains the LH-RH derivative or its salt in an amount of 12%by weight to 24% by weight based on the sustained release composition;(14) the sustained release composition according to the above-mentioned(1), wherein the physiologically active substance or its salt is aslightly water-soluble or water-soluble substance;(15) the sustained release composition according to the above-mentioned(1) which is a formulation for injection;(16) a method for producing a sustained release composition according tothe above-mentioned (1) which comprises removing a solvent from amixture of a pharmacologically active substance or its salt, a lacticacid-glycolic acid polymer or its salt and a hydroxynaphthoic acid orits salt;(17) the method according to the above-mentioned (16) which comprisesmixing the pharmacologically active substance or its salt with asolution of the lactic acid-glycolic acid polymer or its salt and thehydroxynaphthoic acid or its salt in an organic solvent, dispersing themixture, and then removing the organic solvent;(18) the method according to the above-mentioned (16), wherein thepharmacologically active substance or its salt is an aqueous solutioncontaining the pharmacologically active substance or its salt;(19) the method according to the above-mentioned (16), wherein the saltof the pharmacologically active substance is a salt with a free base oracid;(20) a medicament comprising a sustained release composition accordingto the above-mentioned (1);(21) a prophylactic or therapeutic agent against prostate cancer,prostate hyperplasia, endometriosis, hysteromyoma, metrofibroma,precocious puberty, dysmenorrhea or mammary cancer or an contraceptivecontaining a sustained release composition according to theabove-mentioned (3);(22) the sustained release composition according to the above-mentioned(1), wherein the pharmacologically active substance or its salt isreleased over a period of at least 6 months or longer; and(23) a sustained release composition comprising a pharmacologicallyactive substance or its salt, 1-hydroxy-2-naphthoic acid or its salt anda biodegradable polymer or its salt.

Furthermore, the invention provides:

(24) a method for producing a sustained release composition according tothe above-mentioned (16) which comprises producing a w/o emulsion havingas an inner aqueous phase a liquid containing the physiologically activesubstance or its salt and as an oil phase a solution containing thelactic acid-glycolic acid or its salt and the hydroxynaphthoic acid orits salt followed by removing a solvent;

(25) a method for producing a sustained release composition according tothe above-mentioned (16) which comprises producing a w/o emulsion havingas an inner aqueous phase a liquid containing the hydroxynaphthoic acidor its salt and as an oil phase a solution containing thephysiologically active substance or its salt and the lacticacid-glycolic acid or its salt followed by removing a solvent;

(26) a method for producing a sustained release composition according tothe above-mentioned (16) which comprises mixing the pharmacologicallyactive substance or its salt with the hydroxynaphthoic acid or its salt,dissolving the mixture, and then removing the organic solvent; and

(27) a method for producing a sustained release composition according toany of the above-mentioned (24) to (26) wherein the process for removingthe solvent is a in-water drying method.

While a physiologically active substance employed in the presentinvention is not limited particularly as long as it is pharmaceuticallyuseful, it may be a non-peptide compound or a peptide compound. Anon-peptide compound may for example be an agonist, an antagonist and acompound having an inhibitory effect on an enzyme. An example of apreferred peptide compound is a physiologically active peptide having amolecular weight of about 300 to about 40,000, preferably about 400 toabout 30,000, more preferably about 500 to about 20,000.

Such physiologically active peptide may for example be luteinizationhormone-releasing hormone (LH-RH), insulin, somatostatin, growthhormone, growth hormone-releasing hormone (GH-RH), prolactin,erythropoietin, adrenocortical hormone, melanocyte-stimulating hormone,thyroid hormone-releasing hormone, thyroid-stimulating hormone,luteinization hormone, follicle-stimulating hormone, vasopressin,oxytocin, calcitonin, gastrin, serectin, pancreozymin, cholecystokinin,angiotensin, human placental lactogen, human chorionic gonadotropin,enkephalin, endorphin, L-tyrosil, L-arginine, “KYOTORPHIN”, tuftsin,thymopoietin, thymosin, “THYMOTHYMRIN”, thymic humoral factor, bloodthymic factor, tumor necrosis factor, colony-inducing factor, motilin,“DEINORPHINE”, bombesin, neurotensin, cerulein, bradykinin, atrialnatriuretic factor, nerve growth factor, cell growth factor,neurotrophic factor, endothelin-antagonizing peptide and theirderivatives as well as their fragments and derivative thereof.

In the present invention, a physiologically active substance may beemployed as it is or as a pharmaceutically acceptable salt thereof.

A salt of a physiologically active substance having a basic group suchas an amino group may for example be a salt with an inorganic acid(referred to also as an inorganic free acid) (e.g., carbonic acid,bicarbonic acid, hydrochloric acid, sulfuric acid, nitric acid, boricacid and the like) and with an organic acid (referred to also as anorganic free acid) (e.g., succinic acid, acetic acid, propionic acid,trofluoroacetic acid and the like).

A salt of a physiologically active substance having an acidic group suchas a carboxyl group may for example be a salt with an inorganic base(referred to also as an inorganic free base) (e.g., an alkaline metalsuch as sodium and potassium, an alkaline earth metal such as calciumand magnesium) or with an organic base (referred to also as an inorganicfree base) (e.g., an organic amine such as triethylamine, a basic aminoacid such as arginine). A physiologically active peptide may form ametal complex compound (e.g., copper complex, zinc complex and the like.

A preferred example of such physiologically active peptide is an LH-RHderivative or its salt which is useful for treating a hormone-dependentdisease, especially a sex hormone-dependent cancer (e.g., prostatecancer, uterine cancer, mammary cancer, pituitary cancer and the like),a sex hormone-dependent disease such as prostate hyperplasia,endometriosis, hysteromyoma, precocious puberty, dysmenorrhea,amenorrhea, premenstrual syndrome, multilocular ovarian syndrome and thelike, and useful as a contraceptive (or against infertility whenutilizing a rebound effect after discontinuation). Also exemplified isan LH-RH derivative or its salt which is useful for treating a benign ormalignant tumor which is not sex hormone-dependent but is LH-RHsensitive.

Typically, an LH-RH derivative or its salt may for example be thepeptides described in Treatment with GnRH analogs: Controvesies andperspectives, The Parthenon Publishing Group Ltd., (1996),JP-W-3-503165, JP-A-3-101695, 7-97334 and 8-259460.

An LH-RH derivative may for example be an LH-RH agonist or an LH-RHantagonist, the latter may for example be a pharmacologically activepeptide represented by Formula [I]:X-D2Nal-D4ClPhe-D3Pal-Ser-A-B-Leu-C-Pro-DAlaNH₂Wherein X denotes N(4H2-furoyl)Gly or NAc, A denotes a residue selectedfrom NMeTyr, Tyr, Aph(Atz) and NMeAph(Atz), B denotes a residue selectedfrom DLys(Nic), DCit, DLys(AzaglyNic), DLys(AzaglyFur), DhArg(Et₂),DAph(Atz) and DhCi, and C denotes Lys(Nisp), Arg or hArg(Et₂) or itssalt.

An LH-RH agonist may for example be a pharmacologically active peptiderepresented by Formula [II]:5-oxo-Pro-His-Trp-Ser-Tyr-Y-Leu-Arg-Pro-Zwherein Y denotes a residue selected from DLeu, DAla, DTrp, DSer(tBu),D2NaI and DHis(ImBzl), and Z denotes NH—C₂H₅ or Gly-NH₂ or its salt. Onepreferred especially is a peptide wherein Y is DLeu, Z is NH—C₂H₅ (i.e.,a peptide represented by5-oxo-Pro-His-Trp-Ser-Tyr-DLeu-Leu-Arg-Pro-NH—C₂H₅).

Any of these peptides can be produced by a method described in theforegoing references and specifications as well as a method inaccordance therewith.

Abbreviations employed herein are listed below. Abbreviation NameN(4H2-furoyl)Gly: N-tetrahydrofuroyl glycine residue NAc: N-acetyl groupD2Nal: D-3-(2-naphthyl)alanine residue D4ClPhe:D-3-(4-chloro)phenylalanine residue D3Pal: D-3-(3-pyridyl)alanineresidue NMeTyr: N-methyltyrosine residue Aph(Atz):N-[5′-(3′-amino-1′H-1′,2′,4′-triazolyl)]- phenylalanine residueNmeAph(Atz): N-methyl-[5′-(3′-amino-1′H-1′,2′,4′-triazolyl)]phenylalanine residue DLys(Nic): D-(e-N-nicotinoyl)lysineresidue Dcit: D-citrulline residue DLys(AzaglyNic):D-(azaglycylnicotinoyl)lysine residue DLys(AzaglyFur):D-(azaglycylfuranyl)lysine residue DhArg(Et₂):D-(N,N′-diethyl)homoarginine residue Daph(Atz):D-N-[5′-(3′-amino-1′H-1′,2′,4′- triazolyl)]phenylalanine residue DhCi:D-homocitrulline residue Lys(Nisp): (e-N-isopropyl)lysine residuehArg(Et₂): (N,N′-diethyl)homoarginine residue DSer(tBu):O-tert-butyl-D-serine Dhis(ImBzl): N^(im)-benzyl-D-histidine

Otherwise, an amino acid, when designated as an abbreviation, isrepresented as found in IUPAC-IUB Commission on BiochemicalNomenclature, European Journal of Biochemistry, Vol. 138, page 9 to 37(1984) or as customary in the art, and an amino acid, even when opticalisomers thereof exist, means an L form unless otherwise specified.

A hydroxynaphthoic acid employed in the invention is a naphthalene towhich one hydroxyl group and one carboxyl group were bound on differentcarbon atoms. Accordingly, there were 14 isomers in total which differfrom each other in the position of the hydroxyl group in relation toeach of the 1-position and the 2-position at which the carboxyl group isbound to the naphthalene ring. The invention may employ any of theseisomers as well as a mixture thereof at any ratio. As described below,one having a higher acid dissociation constant is preferable, or onehaving a lower pKa (pKa=−log 10 Ka wherein Ka is an acid dissociationconstant is preferable. A slightly water-soluble isomer is preferable.

One also preferred is an isomer which is soluble in an alcohol (forexample, ethanol and methanol). The expression “soluble in an alcohol”means that the solubility, for example in methanol, is 10 g/L or higher.

While the pKa of 3-hydroxy-2-naphthoic acid (pKa=2.708, KAGAKUBINRAN,II, NIPPON KAGAKUKAI, Published on Sep. 25, 1969) is the only known pKaamong hydroxynaphthoic acid isomers, a comparison of the pKa between thethree isomers of hydroxybenzoic acid serves to give a usefulinformation. Thus, the pKas of m-hydroxybenzoic acid andp-hydroxybenzoic acid are 4 or higher, while the pKa of o-hydroxybenzoicacid (salicylic acid) is far lower (=2.754). Accordingly,3-hydroxy-2-naphthoic acid, 1-hydroxy-2-naphthoic acid and2-hydroxy-1-naphthoic acid each having a carboxyl group and a hydroxylgroup bound to the adjacent carbon atoms in the naphthalene ring arepreferred among the 14 isomers described above.

A hydroxynaphthoic acid may be a salt. Such salt may for example be asalt with an inorganic base (e.g., an alkaline metal such as sodium andpotassium, an alkaline earth metal such as calcium and magnesium), withan organic base (e.g., an organic amine such as triethylamine, a basicamino acid such as arginine), or with a transition metal (e.g., zinc,iron, copper) as well as a complex salt.

An example of a method for producing a hydroxynaphthoate of apharmaceutically active substance of the invention is described below.

(1) A solution of a hydroxynaphthoic acid in a hydrated organic solventis loaded onto and adsorbed by a weakly basic ion exchange column untilsaturation. Subsequently, the hydrated organic solvent is loaded toremove excessive hydroxynaphthoic acid and then a solution of aphysiologically active substance or its salt in a hydrated organicsolvent is loaded to effect an ion exchange, and the resultant effluentis made free of the solvent. Such hydrated organic solvent contains asan organic solvent an alcohol (e.g., methanol, ethanol), acetonitrile,tetrahydrofuran, dimethylformamide and the like. A method for removingthe solvent to precipitate a salt may be a method known per se or amethod in accordance therewith. For example, the solvent is evaporatedoff with adjusting the vacuum level using a rotary evaporator.

(2) The exchange ion of a strongly basic ion exchange column haspreviously been replaced with a hydroxide ion and then is loaded with asolution of a physiologically active substance or its salt in a hydratedorganic solvent whereby exchanging the basic groups into the hydroxides.The recovered effluent was used to dissolve a hydroxynaphthoic acid inan amount less than the equivalent, concentrated to precipitate a salt,which is dried if necessary after washing with water.

Since a hydroxynaphthoate of a physiologically active substance isslightly water-soluble although the solubility may vary depending on thephysiologically active substance employed, it can be used as a sustainedrelease formulation utilizing the sustained releasing ability of thephysiologically active peptide salt itself or it can further beformulated into a sustained release composition.

A lactic acid-glycolic acid polymer employed in the invention is alactic acid-glycolic acid polymer whose weight average molecular weightmultiplied by the amount (μmol) of the terminal carboxyl group per unitmass (g) of the lactic acid-glycolic acid polymer is 1,200,000 to3,000,000 (inclusive), preferably 1,500,000 to 2,600,000 (inclusive),with one having a terminal free carboxyl group being employedpreferably.

A lactic acid-glycolic acid polymer may be in the form of a salt. Suchsalt may for example be a salt with an inorganic base (e.g., an alkalinemetal such as sodium and potassium, an alkaline earth metal such ascalcium and magnesium), with an organic base (e.g., an organic aminesuch as triethylamine, a basic amino acid such as arginine), or with atransition metal (e.g., zinc, iron, copper) as well as a complex salt.

Such polymer has a % molar ratio between lactic acid and glycolic acidranging preferably from about 100/0 to about 40/60, more preferably fromabout 100/0 to about 50/50. A lactic acid homopolymer whose % molarratio is 100/0 is also employed preferably.

The optical isomer ratio of lactic acid which is one of the leastrepeating units of “lactic acid-glycolic acid polymer” described above,when represented as D-form/L-form (% mol/mol), is preferably about 75/25to about 25/75. Those having a ratio of D-form/L-form (% mol/mol)especially of about 60/40 to about 30/70 are employed frequently.

The weight average molecular weight of “lactic acid-glycolic acidpolymer” described above is usually about 3,000 to about 100,000,preferably about 3,000 to about 60,000, more preferably about 3,000 toabout 50,000, especially about 20,000 to about 50,000.

A lactic acid-glycolic acid polymer of the invention may for example bea polymer having a weight average molecular weight multiplied by theamount (μmol) of the terminal carboxyl group per unit mass (g) of thelactic acid-glycolic acid polymer of 1,200,000 to 3,000,000 (inclusive),more preferably a polymer having a weight average molecular weightmultiplied by the amount (μmol) of the terminal carboxyl group per unitmass (g) of the lactic acid-glycolic acid polymer of 1,500,000 to2,600,000 (inclusive).

The polydispersity (weight average molecular weight/number averagemolecular weight) is usually about 1.2 to about 4.0, preferably about1.5 to about 3.5, more preferably about 1.7 to about 3.0.

The amount of the free carboxyl group of “lactic acid-glycolic acidpolymer” described above per unit mass (g) of the polymer is usuallyabout 20 to about 1000 μmol, more preferably about 40 to about 1000μmol. A further preferable amount is about 40 to about 95 μmol,especially about 50 to about 90 μmol.

Preferred examples are:

(1) a lactic acid-glycolic acid polymer whose weight average molecularweight is about 3,000 to about 100,000 and whose weight averagemolecular weight multiplied by the amount (μmol) of the terminalcarboxyl group per unit mass (g) of the lactic acid-glycolic acidpolymer is 1,200,000 to 3,000,000 (inclusive);

(2) a lactic acid-glycolic acid polymer whose weight average molecularweight is about 3,000 to about 60,000 and whose weight average molecularweight multiplied by the amount (μmol) of the terminal carboxyl groupper unit mass (g) of the lactic acid-glycolic acid polymer is 1,200,000to 3,000,000 (inclusive);

(3) a lactic acid-glycolic acid polymer whose weight average molecularweight is about 3,000 to about 50,000 and whose weight average molecularweight multiplied by the amount (μmol) of the terminal carboxyl groupper unit mass (g) of the lactic acid-glycolic acid polymer is 1,200,000to 3,000,000 (inclusive);

(4) a lactic acid-glycolic acid polymer whose weight average molecularweight is about 20,000 to about 50,000 and whose weight averagemolecular weight multiplied by the amount (μmol) of the terminalcarboxyl group per unit mass (g) of the lactic acid-glycolic acidpolymer is 1,200,000 to 3,000,000 (inclusive);

(5) a lactic acid-glycolic acid polymer whose amount (μmol) of theterminal carboxyl group per unit mass (g) of the lactic acid-glycolicacid polymer is about 20 to about 1000 μmol and whose weight averagemolecular weight multiplied by the amount (μmol) of the terminalcarboxyl group per unit mass (g) of the lactic acid-glycolic acidpolymer is 1,200,000 to 3,000,000 (inclusive);

(6) a lactic acid-glycolic acid polymer whose amount (μmol) of theterminal carboxyl group per unit mass (g) of the lactic acid-glycolicacid polymer is about 40 to about 1000 μmol and whose weight averagemolecular weight multiplied by the amount (μmol) of the terminalcarboxyl group per unit mass (g) of the lactic acid-glycolic acidpolymer is 1,200,000 to 3,000,000 (inclusive);

(7) a lactic acid-glycolic acid polymer [1] whose weight averagemolecular weight is about 3,000 to about 100,000, [2] whose amount(μmol) of the terminal carboxyl group per unit mass (g) of the lacticacid-glycolic acid polymer is about 20 to about 1000 μmol and [3] whoseweight average molecular weight multiplied by the amount (μmol) of theterminal carboxyl group per unit mass (g) of the lactic acid-glycolicacid polymer is 1,200,000 to 3,000,000 (inclusive);

(8) a lactic acid-glycolic acid polymer [1] whose weight averagemolecular weight is about 3,000 to about 100,000, [2] whose amount(μmol) of the terminal carboxyl group per unit mass (g) of the lacticacid-glycolic acid polymer is about 40 to about 1000 μmol and [3] whoseweight average molecular weight multiplied by the amount (μmol) of theterminal carboxyl group per unit mass (g) of the lactic acid-glycolicacid polymer is 1,200,000 to 3,000,000 (inclusive);

(9) a lactic acid-glycolic acid polymer [1] whose weight averagemolecular weight is about 3,000 to about 60,000, [2] whose amount (μmol)of the terminal carboxyl group per unit mass (g) of the lacticacid-glycolic acid polymer is about 20 to about 1000 μmol and [3] whoseweight average molecular weight multiplied by the amount (μmol) of theterminal carboxyl group per unit mass (g) of the lactic acid-glycolicacid polymer is 1,200,000 to 3,000,000 (inclusive);

(10) a lactic acid-glycolic acid polymer [1] whose weight averagemolecular weight is about 3,000 to about 60,000, [2] whose amount (μmol)of the terminal carboxyl group per unit mass (g) of the lacticacid-glycolic acid polymer is about 40 to about 1000 μmol and [3] whoseweight average molecular weight multiplied by the amount (μmol) of theterminal carboxyl group per unit mass (g) of the lactic acid-glycolicacid polymer is 1,200,000 to 3,000,000 (inclusive);

(11) a lactic acid-glycolic acid polymer [1] whose weight averagemolecular weight is about 3,000 to about 50,000, [2] whose amount (μmol)of the terminal carboxyl group per unit mass (g) of the lacticacid-glycolic acid polymer is about 20 to about 1000 μmol and [3] whoseweight average molecular weight multiplied by the amount (μmol) of theterminal carboxyl group per unit mass (g) of the lactic acid-glycolicacid polymer is 1,200,000 to 3,000,000 (inclusive);

(12) a lactic acid-glycolic acid polymer [1] whose weight averagemolecular weight is about 3,000 to about 50,000, [2] whose amount (μmol)of the terminal carboxyl group per unit mass (g) of the lacticacid-glycolic acid polymer is about 40 to about 1000 μmol and [3] whoseweight average molecular weight multiplied by the amount (μmol) of theterminal carboxyl group per unit mass (g) of the lactic acid-glycolicacid polymer is 1,200,000 to 3,000,000 (inclusive);

(13) a lactic acid-glycolic acid polymer [1] whose weight averagemolecular weight is about 20,000 to about 50,000, [2] whose amount(μmol) of the terminal carboxyl group per unit mass (g) of the lacticacid-glycolic acid polymer is about 20 to about 1000 μmol and [3] whoseweight average molecular weight multiplied by the amount (μmol) of theterminal carboxyl group per unit mass (g) of the lactic acid-glycolicacid polymer is 1,200,000 to 3,000,000 (inclusive); and

(14) a lactic acid-glycolic acid polymer [1] whose weight averagemolecular weight is about 20,000 to about 50,000, [2] whose amount(μmol) of the terminal carboxyl group per unit mass (g) of the lacticacid-glycolic acid polymer is about 40 to about 1000 μmol and [3] whoseweight average molecular weight multiplied by the amount (μmol) of theterminal carboxyl group per unit mass (g) of the lactic acid-glycolicacid polymer is 1,200,000 to 3,000,000 (inclusive).

More preferred example are:

(15) a lactic acid-glycolic acid polymer [1] whose weight averagemolecular weight is about 3,000 to about 100,000 and [2] whose weightaverage molecular weight multiplied by the amount (μmol) of the terminalcarboxyl group per unit mass (g) of the lactic acid-glycolic acidpolymer is 1,500,000 to 2,600,000 (inclusive);

(16) a lactic acid-glycolic acid polymer [1] whose weight averagemolecular weight is about 3,000 to about 60,000 and [2] whose weightaverage molecular weight multiplied by the amount (μmol) of the terminalcarboxyl group per unit mass (g) of the lactic acid-glycolic acidpolymer is 1,500,000 to 2,600,000 (inclusive);

(17) a lactic acid-glycolic acid polymer [1] whose weight averagemolecular weight is about 3,000 to about 50,000 and [2] whose weightaverage molecular weight multiplied by the amount (μmol) of the terminalcarboxyl group per unit mass (g) of the lactic acid-glycolic acidpolymer is 1,500,000 to 2,600,000 (inclusive);

(18) a lactic acid-glycolic acid polymer [1] whose weight averagemolecular weight is about 20,000 to about 50,000 and [2] whose weightaverage molecular weight multiplied by the amount (μmol) of the terminalcarboxyl group per unit mass (g) of the lactic acid-glycolic acidpolymer is 1,500,000 to 2,600,000 (inclusive);

(19) a lactic acid-glycolic acid polymer [1] whose amount (μmol) of theterminal carboxyl group per unit mass (g) of the lactic acid-glycolicacid polymer is about 20 to about 1000 μmol and [2] whose weight averagemolecular weight multiplied by the amount (μmol) of the terminalcarboxyl group per unit mass (g) of the lactic acid-glycolic acidpolymer is 1,500,000 to 2,600,000 (inclusive);

(20) a lactic acid-glycolic acid polymer [1] whose amount (μmol) of theterminal carboxyl group per unit mass (g) of the lactic acid-glycolicacid polymer is about 40 to about 1000 μmol and [2] whose weight averagemolecular weight multiplied by the amount (μmol) of the terminalcarboxyl group per unit mass (g) of the lactic acid-glycolic acidpolymer is 1,500,000 to 2,600,000 (inclusive);

(21) a lactic acid-glycolic acid polymer [1] whose weight averagemolecular weight is about 3,000 to about 100,000 and [2] whose amount(μmol) of the terminal carboxyl group per unit mass (g) of the lacticacid-glycolic acid polymer is about 20 to about 1000 μmol and [3] whoseweight average molecular weight multiplied by the amount (μmol) of theterminal carboxyl group per unit mass (g) of the lactic acid-glycolicacid polymer is 1,500,000 to 2,600,000 (inclusive);

(22) a lactic acid-glycolic acid polymer [1] whose weight averagemolecular weight is about 3,000 to about 100,000 and [2] whose amount(μmol) of the terminal carboxyl group per unit mass (g) of the lacticacid-glycolic acid polymer is about 40 to about 1000 μmol and [3] whoseweight average molecular weight multiplied by the amount (μmol) of theterminal carboxyl group per unit mass (g) of the lactic acid-glycolicacid polymer is 1,500,000 to 2,600,000 (inclusive);

(23) a lactic acid-glycolic acid polymer [1] whose weight averagemolecular weight is about 3,000 to about 60,000 and [2] whose amount(μmol) of the terminal carboxyl group per unit mass (g) of the lacticacid-glycolic acid polymer is about 20 to about 1000 μmol and [3] whoseweight average molecular weight multiplied by the amount (μmol) of theterminal carboxyl group per unit mass (g) of the lactic acid-glycolicacid polymer is 1,500,000 to 2,600,000 (inclusive);

(24) a lactic acid-glycolic acid polymer [1] whose weight averagemolecular weight is about 3,000 to about 60,000 and [2] whose amount(μmol) of the terminal carboxyl group per unit mass (g) of the lacticacid-glycolic acid polymer is about 40 to about 1000 μmol and [3] whoseweight average molecular weight multiplied by the amount (μmol) of theterminal carboxyl group per unit mass (g) of the lactic acid-glycolicacid polymer is 1,500,000 to 2,600,000 (inclusive);

(25) a lactic acid-glycolic acid polymer [1] whose weight averagemolecular weight is about 3,000 to about 50,000 and [2] whose amount(μmol) of the terminal carboxyl group per unit mass (g) of the lacticacid-glycolic acid polymer is about 20 to about 1000 μmol and [3] whoseweight average molecular weight multiplied by the amount (μmol) of theterminal carboxyl group per unit mass (g) of the lactic acid-glycolicacid polymer is 1,500,000 to 2,600,000 (inclusive);

(26) a lactic acid-glycolic acid polymer [1] whose weight averagemolecular weight is about 3,000 to about 50,000 and [2] whose amount(μmol) of the terminal carboxyl group per unit mass (g) of the lacticacid-glycolic acid polymer is about 40 to about 1000 μmol and [3] whoseweight average molecular weight multiplied by the amount (μmol) of theterminal carboxyl group per unit mass (g) of the lactic acid-glycolicacid polymer is 1,500,000 to 2,600,000 (inclusive);

(27) a lactic acid-glycolic acid polymer [1] whose weight averagemolecular weight is about 20,000 to about 50,000 and [2] whose amount(μmol) of the terminal carboxyl group per unit mass (g) of the lacticacid-glycolic acid polymer is about 20 to about 1000 μmol and [3] whoseweight average molecular weight multiplied by the amount (μmol) of theterminal carboxyl group per unit mass (g) of the lactic acid-glycolicacid polymer is 1,500,000 to 2,600,000 (inclusive); and,

(28) a lactic acid-glycolic acid polymer [1] whose weight averagemolecular weight is about 20,000 to about 50,000 and [2] whose amount(μmol) of the terminal carboxyl group per unit mass (g) of the lacticacid-glycolic acid polymer is about 40 to about 1000 μmol and [3] whoseweight average molecular weight multiplied by the amount (μmol) of theterminal carboxyl group per unit mass (g) of the lactic acid-glycolicacid polymer is 1,500,000 to 2,600,000 (inclusive).

A weight average molecular weight, a number average molecular weight anda polydispersity mean a molecular weight as polystyrene determined by agel permeation chromatography (GPC) using as standards 15 monodispersepolystyrenes whose weight average molecular weights are 1,110,000,707,000, 455,645, 354, 000, 189, 000, 156,055, 98, 900, 66, 437, 37,200, 17, 100, 9,830, 5,870, 2,500, 1,303 and 504 and a polydispersitycalculated therefrom. The determination is performed using a high speedGPC instrument (TOSO, HLC-8120GPC, detection by differential refractiveindex) together with a GPC column KF804Lx2 (SHOWA DENKO) and chloroformas a mobile phase. The flow rate is 1 ml/min.

An amount of a free carboxyl group mentioned here means an amountdetermined by a labeling method (hereinafter referred to as a labelingmethod-based carboxyl group level). Typically, in the case of apolylactic acid, W mg of the polylactic acid is dissolved in 2 ml of amixture of 5N hydrochloric acid/acetonitrile (v/v=4/96) and combinedwith 2 ml of a 0.01 M solution of o-nitrophenylhydrazine hydrochloride(ONPH) (5N hydrochloric acid/acetonitrile/ethanol=1.02/35/15) and 2 mlof a 0.15M solution of 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimidehydrochloride (pyridine/ethanol=4v/96v), and after allowing the mixtureto react at 40° C. for 30 minutes and then the solvent is distilled off.The residue is washed with water (4 times), dissolved in 2 ml ofacetonitrile, combined with 1 ml of a 0.5 mol/L ethanolic solution ofpotassium hydroxide, and allowed to react at 60° C. for 30 minutes. Thereaction mixture is diluted with a 1.5 N aqueous solution of sodiumhydroxide to make Y ml, which is examined for the absorbance at 544 nmA(/cm) using a 1.5 N aqueous solution of sodium hydroxide as a referencestandard. On the other hand, a n aqueous solution of DL-lactic acid isused as a standard to examine for its free carboxyl group C mol/L bymeans of an alkali titration, and subjected to an ONPH labeling methodto convert into DL-lactic acid hydrazide, which is then examined for theabsorbance at 544 nm B(/cm), based on which the molar amount of the freecarboxyl group per unit mass)g) of the polymer is calculated inaccordance with the following equation.[COOH]=(mol/g)=(AYC)/(WB)

This “amount of the carboxyl group” can be obtained also by dissolving alactic acid-glycolic acid polymer in a solvent mixture oftoluene-acetone-methanol and titrating the resultant solution for thecarboxyl group with an alcoholic solution of potassium hydroxide usingphenolphthalein as an indicator (hereinafter a value obtained by thismethod is referred to as “alkali titration-based carboxyl group level”).

Since the rate at which a lactic acid-glycolic acid polymer is degradedand disappears is reduced usually at a reduced ratio of glycolic acidalthough it may vary greatly depending on the copolymer composition, themolecular weight or the free carboxyl group level, it is possible toprolong the release duration by means of reducing the glycolic acidratio or increasing the molecular weight simultaneously with reducingthe free carboxyl group level.

Such “lactic acid-glycolic acid polymer” can be produced for example bya non-catalytic dehydrative condensation polymerization (JP-A-61-28521)from lactic acid and glycolic acid or by a ring-opening polymerizationfrom cyclic diester compounds such as lactides and glycolides(Encyclopedic Handbook of Biomaterials and Bioengineering Part A:Materials, Volume 2, Marcel Dekker, Inc, 1995). While a polymer obtainedby the known ring-opening polymerization described above may sometimesbe a polymer having no free carboxyl group at its terminal, such polymercan be converted into a polymer having a certain amount of the carboxylgroup per unit mass for example by means of hydrolysis described inEP-A-0839525 prior to its use.

“Lactic acid-glycolic acid polymer having a terminal free carboxylgroup” can readily be produced by a known method (for example, anon-catalytic dehydrative condensation polymerization, JP-A-61-28521) orby the following methods.

(1) First, a cyclic ester compound is subjected to a polymerizationusing a polymerization catalyst in the presence of a carboxyl-protectedhydroxymonocarboxylic acid derivative (e.g. t-butyl D-lactate, benzylL-lactate) or a carboxyl-protected hydroxydicarboxylic acid derivative(e.g., dibenzyl tartronate, di-t-butyl dihydroxyethylmalonate).

“Carboxyl-protected hydroxymonocarboxylic acid derivative” or“carboxyl-protected hydroxydicarboxylic acid derivative” mentioned abovemay for example be a hydroxycarboxylic acid derivative whose carboxylgroup (—COOH) is amidated (—CONH₂) or esterified (—COOR), with ahydroxycarboxylic acid derivative whose carboxyl group (—COOH) isesterified (—COOR) being preferred.

R in an ester mentioned here may for example be a C₁₋₆ alkyl group suchas methyl, ethyl, n-propyl, isopropyl, n-butyl and t-butyl, a C₃₋₈cycloalkyl group such as cyclopentyl and cyclohexyl, a C₆₋₁₂ aryl groupsuch as phenyl and α-naphthyl, a C₇₋₁₄ aralkyl group including aphenyl-C₁₋₂ alkyl group such as benzyl and phenethyl or anα-naphthyl-C₁₋₂ alkyl group such as α-naphthylmethyl. Among those listedabove, a t-butyl group and a benzyl group are preferred.

“Cyclic ester compound” mentioned above may for example be a cycliccompound having at least one ester bond within the ring. Those which areexemplified typically are a cyclic monoester compound (lactone) and acyclic diester compound (lactide).

“Cyclic monoester compound” mentioned above may for example be a4-membered cyclic lactone (β-propiolactone, β-butyrolactone,β-isovalerolactone, β-caprolactone, β-isocaprolactone,β-methyl-β-valerolactone and the like), a 5-membered cyclic lactone(γ-butyrolactone, γ-valerolactone and the like), a δ-membered cycliclactone (δ-valerolactone and the like), a 7-membered cyclic lactone(ε-caprolactone and the like), p-dioxanone, 1,5-dioxepan-2-one and thelike.

“Cyclic diester compound” mentioned above may for example be a compoundrepresented by Formula:

wherein R¹ and R² are the same or different and each denotes a hydrogenatom or a C₁₋₆ alkyl group such as methyl, ethyl, n-propyl, isopropyl,n-butyl and t-butyl), and a lactide wherein R¹ is a hydrogen atom and R²is a methyl group or each of R¹ and R² is a hydrogen atom.

Those exemplified typically are glycolide, L-lactide, D-lactide,DL-lactide, meso-lactide, 3-methyl-1,4-dioxane-2,5-dione (includingoptical isomers) and the like.

“Polymerization catalyst” mentioned above may for example be an organictin-based catalyst (e.g., tin octylate, di-n-butyltin dilaurate,tetraphenyltin), an aluminum-based catalyst (e.g., triethylaluminum) anda zinc-based catalyst (e.g., diethylzinc).

Aluminum-based and zinc-based catalysts are preferred for the purpose ofremoving a solvent easily after a reaction, while a zinc-based catalystis preferred for the purpose of ensuring the safety of residual catalystif any.

A solvent for a polymerization catalyst is benzene, hexane, toluene andthe like, with hexane and toluene being preferred especially.

“Polymerization method” may be a bulk polymerization in which a reactantis used as being melted or a solution polymerization in which a reactantis employed as being dissolved in a suitable solvent (for example,benzene, toluene, xylene, decalin, and dimethylformamide). A preferredsolvent is toluene, xylene and the like. While the polymerizationtemperature is not limited particularly, a bulk polymerization mayemploy a temperature capable of melting a reactant at the initiation ofthe reaction or higher, usually 100 to 300° C., and a solutionpolymerization usually employs room temperature to 150° C. with using acondenser for reflux or a pressure-resistant reactor when the reactiontemperature exceeds the boiling point of the reaction solution. Whilethe polymerization time period may vary depending on the polymerizationtemperature, other reaction conditions and intended polymercharacteristics, it may for example be 10 minutes to 72 hours.

After the reaction, the reaction mixture is dissolved in a suitablesolvent (for example, acetone, dichloromethane, chloroform), combinedwith an acid (for example, hydrochloric acid, acetic anhydride,trifluoroacetic acid) to terminate the polymerization, and thenprecipitated for example by mixing with a solvent which does notdissolve an intended product (for example, alcohol, water, ether,isopropyl ether) in accordance with a standard method, whereby isolatinga lactic acid-glycolic acid polymer having a protected carboxyl group atits ω-terminal.

A polymerization method according to the invention employs acarboxyl-protected hydroxycarboxylic acid derivative (e.g., t-butylD-lactate, benzyl L-lactate) or a carboxyl-protected hydroxydicarboxylicacid derivative (e.g., dibenzyl tartronate, di-t-butyldihydroxyethylmalonate) instead of a protonic chain transfer agent suchas methanol employed conventionally.

By using such carboxyl-protected hydroxycarboxylic acid derivative(e.g., t-butyl D-lactate, benzyl L-lactate) or carboxyl-protectedhydroxydicarboxylic acid derivative (e.g., dibenzyl tartronate,di-t-butyl dihydroxyethylmalonate) as a protonic chain transfer agent,[1] it is possible to control the molecular weight on the basis of theinput composition, and [2] a deprotection after the polymerizationserves to make the carboxyl group free at the ω-terminal of theresultant lactic acid-glycolic acid polymer.

(2) Subsequently, a lactic acid-glycolic acid polymer having a protectedcarboxyl group at its ω-terminal obtained by the polymerization inabove-mentioned (1) is deprotected to obtain an intended lacticacid-glycolic acid polymer having a free carboxyl group at itsω-terminal.

A protecting group can be deprotected by a method known per se. Whilethe method may be any method as long as it can remove the protectivegroup without affecting the ester bond of a poly(hydroxycarboxylic acid)adversely, it may typically be a reduction, an acid decomposition andthe like.

A reduction method may for example be a catalytic hydrogenation using acatalyst (e.g., palladium on carbon, palladium black, platinum oxide), areduction with sodium in a liquid ammonium and a reduction withdithiothreitol. In the case for example that a polymer having a carboxylgroup protected by a benzyl group at its ω-terminal is hydrogenatedcatalytically, the polymer dissolved typically in ethyl acetate,dichloromethan, chloroform and the like is combined with a palladium oncarbon, bubbled with hydrogen with stirring vigorously at roomtemperature for about 20 minutes to about 4 hours, whereby accomplishingdeprotection.

An acid decomposition may for example be an acid decomposition using aninorganic acid (e.g., hydrogen fluoride, hydrogen bromide, hydrogenchloride) or an organic acid (e.g., trifluoroacetic acid,methanesulfonic acid, trifluoromethanesulfonic acid) as well as amixture thereof. If necessary, the acid decomposition may be performedin the presence of a cation scavenger (e.g., anisol, phenol,thioanisol). In the case for example that a polymer having a carboxylgroup protected by a t-butyl group at its ω-terminal is subjected to anacid decomposition, the polymer dissolved typically in dichloromethane,xylene, toluene and the like is combined with trifluoroacetic acid in anappropriate amount or the polymer is dissolved in trifluoroacetic acid,and then the mixture is stirred at room temperature for about 1 hour,whereby accomplishing deprotection.

Preferably, an acid decomposition may also be conducted immediatelyafter a polymerization reaction, and in such case it serves also as apolymerization termination reaction.

Also if necessary, a lactic acid-glycolic acid polymer obtained by adeprotection described above can be subjected to an acid hydrolysis toadjust the weight average molecular weight, the number average molecularweight or the terminal carboxyl group level as intended. Typically, amethod described in EP-A-0839525 or a method in accordance therewith maybe employed.

A lactic acid-glycolic acid polymer obtained as described above can beused as a base for producing a sustained release formulation.

A polymer having a non-specific free carboxyl group at its terminal canbe produced by a known method (for example, see WO94/15587).

Furthermore, a lactic acid-glycolic acid polymer whose terminal has beenconverted into a free carboxyl group by means of a chemical treatmentafter a ring-opening polymerization is available commercially forexample from Boehringer Ingelheim KG.

A lactic acid-glycolic acid polymer may be present as a salt (such asthose listed above), which can be produced for example by (a) a methodin which a lactic acid-glycolic acid polymer having a carboxyl groupdescribed above dissolved in an organic solvent is combined with anaqueous solution containing an inorganic base (e.g., an alkaline metalsuch as sodium and potassium, an alkaline earth metal such as calciumand magnesium) or with an organic base (e.g., an organic amine such astriethylamine, a basic amino acid such as arginine) to effect an ionexchanging reaction, followed by an isolation of the polymer as a salt,(b) a method in which a weak acid salt of a base listed inabove-mentioned (a) (for example, acetate and glycolate) is dissolved ina solution of a lactic acid-glycolic acid polymer having a carboxylgroup described above in an organic solvent and then the lacticacid-glycolic acid polymer in the form of a salt is isolated, (c) amethod in which a lactic acid-glycolic acid polymer having a carboxylgroup described above dissolved in an organic solvent is combined with aweak acid salt (for example, acetate and glycolate) or an oxide of atransition metal (e.g., zinc, iron, copper) and then the lacticacid-glycolic acid polymer in the form of a salt is isolated.

While the weight ratio of a pharmacologically active substance in acomposition of the invention may vary depending on the type of thepharmacologically active substance, the pharmacological effects desiredand the duration thereof, it is about 0.001 to about 50% by weight,preferably about 0.02 to about 40% by weight, more preferably about 0.1to about 30% by weight, most preferably 12 to 24% by weight in the caseof a physiologically active peptide or its salt based on the totalamount of the physiologically active substance or its salt, ahydroxynaphthoic acid or its salt and a lactic acid-glycolic acidpolymer or its salt when latter three components are contained in asustained release composition, and about 0.01 to about 80% by weight,preferably about 0.1 to about 50% by weight in the case of a non-peptidephysiologically active substance or its salt. Similar ranges of theweight ratio are applicable even when a physiologically active substanceand a hydroxynaphthoic acid are contained. In the case of a sustainedrelease composition comprising a salt of a physiologically activepeptide (designated here as (A)) with a hydroxynaphthoic acid(designated here as (B)), the weight ratio of (A) based on the totalamount of (A)+(B) is usually about 5 to about 90% by weight, preferablyabout 10 to about 85% by weight, more preferably about 15 to about 80%by weight, especially about 30 to about 80% by weight.

In the case of a sustained release composition containing threecomponents, namely, a physiologically active substance or its salt, ahydroxynaphthoic acid or its salt and a lactic acid-glycolic acidpolymer or its salt, the amount of the hydroxynaphthoic acid or its saltper 1 mole of the physiologically active substance or its salt is about½ to about 2 moles, preferably about ¾ to about 4/3 moles, especiallyabout ⅘ to about 6/5 moles.

A procedure for designing a composition of the invention is discussedbelow with referring to a sustained release composition containing threecomponents, namely, a physiologically active substance, ahydroxynaphthoic acid and a lactic acid-glycolic acid polymer in whichthe physiologically active substance is a basic substance. In this case,the composition contains the physiological active substance as a baseand the hydroxynaphthoic acid as an acid, each of which establishes itsdissociation equilibrium in a hydrated state or in the presence of atrace amount of water at any time point during the production of thecomposition in any case that it is incorporated as a free form or a saltinto the composition. Since a salt which a slightly water-solublehydroxynaphthoic acid forms together with a physiologically activesubstance is considered to be slightly water-soluble although thesolubility may vary depending on the physiologically active substanceemployed, the dissociation equilibrium serves favorably for theformation of such slightly water-soluble salt.

In order to produce a composition containing a basic physiologicallyactive substance at a high concentration, it is preferable in view ofthe dissociation equilibrium discussed above to protonate almost all ofthe physiologically active substance to form a slightly water-solublesalt described above. For this purpose, it is preferable that ahydroxynaphthoic acid or its salt in an amount at least almostequivalent to the physiologically active substance or its salt isincorporated.

The mechanism by which a physiologically active substance contained in acomposition is released sustainedly is then discussed below. Thephysiologically active substance has mostly been protonated and existstogether with an accompanying counter ion in the composition describedabove. The counter ion is mainly a hydroxynaphthoic acid. After anadministration of the composition to a living body, the lacticacid-glycolic acid polymer undergoes a degradation to form its oligomersand monomers, and each of the resultant oligomers (lactic acid-glycolicacid oligomers) and monomers (lactic acid or glycolic acid) surely hasone carboxyl group, which can also serves as a counter ion for thephysiologically active substance. While the physiologically activesubstance is released in a manner involving no transfer of an electriccharge, i.e., it is released as a salt accompanied with a counter ion,transferable counter ion species may for example be hydroxynaphthoicacids, lactic acid-glycolic acid oligomers (having transferablemolecular weights) and monomers (lactic acid or glycolic acid).

When two or more acids are present simultaneously, a salt with a strongacid is formed predominantly in general, although the predominance mayvary depending on the ratio. With regard to the pKa of ahydroxynaphthoic acid, the pKa for example of 3-hydroxy-2-naphthoic acidis 2.708 (KAGAKUBINRAN, II, NIPPON KAGAKUKAI, Published on Sep. 25,1969). On the other hand, the pKa of the carboxyl group of a lacticacid-glycolic acid oligomer is not known, but it can be calculated fromthe pKa of lactic acid or glycolic acid (=3.86 or 3.83) in accordancewith the principle that “the change in the free energy by theintroduction of a substituent can be subjected to an approximation onthe basis of addition rule”. The contribution of a substituent to adissociation constant was determined and can be utilized (Table 4.1,“pKa Prediction for Organic Acid and Bases”, D. D. Perrin, B. Dempseyand E. P. Sergeant, 1981). The pKas of a hydroxyl group and an esterbond are represented as follows:

ΔpKa(OH)=−0.90

ΔpKa(ester bond)=−1.7.

Accordingly, the pKa of a carboxyl group in a lactic acid-glycolic acidoligomer, when taking the contribution of an ester bond which is closestto the dissociated group into consideration, is represented as follows:

pKa=pKa(lactic acid or glycolic acid)−ΔpKa(OH)+ΔpKa(ester bond)=3.06 or3.03. Accordingly, a hydroxynaphthoic acid is an acid which is strongerthan lactic acid (pKa=3.86), glycolic acid (pKa=3.83) and the lacticacid-glycolic acid oligomer (pLa=3.83), and thus it is possible that thesalt of the hydroxynaphthoic acid and the physiologically activesubstance is formed predominantly in the composition described above andthat the characteristics of the salt predominantly determines thesustained release profile of the physiologically active substance fromthe composition. A physiologically active substance employed here mayfor example be a physiologically active substance mentioned above.

In this context, the fact that the salt formed from the hydroxynaphthoicacid with the physiologically active substance is slightly water-solublerather than water-insoluble serves favorably for the sustained releasemechanism. Thus, since a predominant existence of a salt of thehydroxynaphthoic acid which is stronger than the lactic acid-glycolicacid oligomer and the monomers among transferable physiologically activesubstance salts at an early stage of the release as evident from thediscussion on the acid dissociation constant described above allows thesolubility and the tissue distribution performance of the salt to bedeterminant factors of a release rate of the physiologically activesubstance, the initial release pattern of the substance can be adjustedon the basis of the amount of the hydroxynaphthoic acid to be added.Subsequently, a decrease in the hydroxynaphthoic acid and an increase inthe oligomers and the monomers formed as a result of the hydrolysis ofthe lactic acid-glycolic acid polymer leads to a gradual predominance ofthe release mechanism of the physiologically active substance whosecounter ions are the oligomers and the monomers, whereby maintaining astable release of the physiologically active substance even after thehydroxynaphthoic acid is depleted substantially from “composition”described above. An increased efficiency in incorporating thephysiologically active substance during the manufacturing process of thesustained release composition and an ability of suppressing an initialexcessive release after an administration of the physiologically activesubstance incorporated can similarly be explained.

Also explained similarly by the mechanism described above is a role of ahydroxynaphthoic acid in a sustained release composition containing ahydroxynaphthoate of a physiologically active peptide.

The term “water-insoluble” used here means that the mass of a substancedissolved in 1 L of a solution after stirring said substance at atemperature of 40° C. or lower in distilled water for 4 hours is 25 mgor less.

The term “slightly water-insoluble” used herein means that the massdescribed above is greater than 25 mg and not greater than 5 g. When therelevant substance is a salt of a physiologically active substance, thenthe mass of the physiologically active substance dissolved in theprocedure described above is subjected to the definition describedabove.

While the morphology of a sustained release composition in the inventionis not limited particularly, it is preferably a microparticle,especially a microsphere (also referred to as a microcapsule in the caseof a sustained release composition containing a lactic acid-glycolicacid polymer). A microsphere mentioned here means an injectablespherical microparticle capable of being dispersed in a solution. Themorphology can be verified for example by an observation using ascanning electron microscope.

A method for producing a an inventive sustained release compositioncomprising a pharmacologically active substance or its salt, ahydroxynaphthoic acid or its salt and a lactic acid-glycolic acidpolymer or its salt is described below with exemplifying a microcapsule.

(I) In-Water Drying Method

(i) O/W Method

In this method, a solution of a hydroxynaphthoic acid or its salt and alactic acid-glycolic acid polymer or its salt in an organic solvent isprepared first. An organic solvent used for producing an inventivesustained release formulation preferably has a melting point of 120° C.or lower.

Such organic solvent may for example be a halogenated hydrocarbon (e.g.,dichloromethane, chloroform, dichloroethane, trichloroethane, carbontetrachloride), an ether (e.g., ethyl ether, isopropyl ether), a fattyacid ester (e.g., ethyl acetate, butyl acetate), an aromatic hydrocarbon(e.g., benzene, toluene, xylene), an alcohol (e.g., ethanol, methanol)as well as acetonitrile. As an organic solvent for a lacticacid-glycolic acid polymer or its salt, dichloromethane is especiallypreferred.

As an organic solvent for the hydroxynaphthoic acid or its salt, analcohol or a mixture of an alcohol and a halogenated hydrocarbon isespecially preferred.

The hydroxynaphthoic acid or its salt and the lactic acid-glycolic acidpolymer or its salt may be dissolved separately and then mixed with eachother, or the both may be dissolved in an organic solvent mixture at acertain ratio. Among the solvents, a mixture of a halogenatedhydrocarbon and an alcohol is employed preferably, with a mixture ofdichloromethane and ethanol being preferred particularly.

The ethanol content in an organic solvent mixture of dichloromethane andethanol when using ethanol as an organic solvent to be mixed withdichloromethane is usually about 0.01 to about 50% (v/v), morepreferably about 0.05 to about 40% (v/v), especially about 0.1 to about30% (v/v).

While the concentration of the lactic acid-glycolic acid polymer in anorganic solvent solution may vary depending on the molecular weight ofthe lactic acid-glycolic acid polymer and the type of the organicsolvent, it is usually about 0.5 to about 70% by weight, more preferablyabout 1 to about 60% by weight, especially about 2 to about 50% byweight, when using dichloromethane as an organic solvent.

The concentration of the hydroxynaphthoic acid or its salt in an organicsolvent, when using a mixture of dichloromethane and ethanol as anorganic solvent, is usually about 0.01 to about 10% by weight, morepreferably about 0.1 to about 5% by weight, especially about 0.5 toabout 3% by weight.

To the solution of the hydroxynaphthoic acid or its salt and the lacticacid-glycolic acid polymer thus obtained, a pharmacologically activesubstance or its salt is added and dissolved or dispersed. Then, theresultant organic solvent solution containing a composition consistingof the pharmacologically active substance or its salt, thehydroxynaphthoic acid or its salt and the lactic acid-glycolic acidpolymer is added to an aqueous phase to form an O(oil phase)/W(aqueousphase) emulsion, and then the solvent in the oil phase is evaporated ordispersed in the aqueous phase, whereby preparing a microcapsule. Thevolume of this aqueous phase is usually about 1 to about 10,000 times,more preferably about 5 to about 50,000 times, especially about 10 toabout 2,000 times the volume of the oil phase.

The outer aqueous phase described above may contain an emulsifier. Suchemulsifier may usually be any emulsifier capable of forming a stable O/Wemulsion. One employed typically is an anionic surfactant (sodiumoleate, sodium stearate, sodium laurylsulfate and the like), a nonionicsurfactant (polyoxyethylene sorbitan fatty acid ester [polyoxyethylene20 sorbitan monooleate sold under the trademark Tween® 80,polyoxyethylene sorbitan monostearate sold under the trademark Tween®60, available from “ATRASPOWDER”], a polyoxyethylene castor oilderivative [polyethylene glycol (PEG)-60 hydrogenated castor oil soldunder the trademark NIKKOL™ HCO-60, polyethylene glycol (PEG)-50hydrogenated castor oil sold under the trademark NIKKOL™ HCO-50,available from “NIKKO CHEMICALS”]), polyvinylpyrrolidone, polyvinylalcohol, carboxymethyl cellulose, lecithin, gelatin, hyaluronic acid andthe like. Any of those listed above may be employed alone or incombination with each other. The concentration is preferably about0.0001 to about 10% by weight, more preferably about 0.001 to about 5%by weight.

To the outer aqueous phase, an osmotic agent may be added.

This osmotic agent may be any substance giving an osmotic pressure in anaqueous solution thereof.

Such osmotic agent may for example be polyhydric alcohol, monohydricalcohol, monosaccharide, disaccharide, oligosaccharide, amino acid aswell as derivatives thereof.

A polyhydric alcohol mentioned above may for example be a trihydricalcohol such as glycerin, a pentahydric alcohol such as arabitol,xylitol and adonitol, a hexahydric alcohol such as mannitol, sorbitoland dulcitol. Among those listed above, a hexahydric alcohol ispreferred, with mannitol being especially preferred.

A monohydric alcohol mentioned above may for example be methanol,ethanol and isopropyl alcohol, with ethanol being preferred.

A monosaccharide mentioned above may for example be a pentose such asarabinose, xylose, ribose and 2-deoxyribose, a hexose such as glucose,fructose, galactose, mannose, sorbose, rhamnose and fucose, with ahexose being preferred.

An oligosaccharide mentioned above may for example be a trisaccharidesuch as maltotriose and raffinose and a tetrasaccharide such asstachyose, with a trisaccharide being preferred.

A derivatives of a monosaccharide, a disaccharide and an oligosaccharidedescribed above may for example be glucosamine, galactosamine,glucuronic acid and galacturonic acid.

An amino acid mentioned above may be any L-amino acid, such as glycine,leucine and arginine. L-Arginine is preferred.

Any of these osmotic agents may be employed alone or in combination witheach other.

Any of these osmotic agents is used at a concentration giving theosmotic pressure of the outer aqueous phase which is about 1/50 to about5 times, preferably about 1/25 to about 3 times the osmotic pressure ofphysiological saline.

A method for removing an organic solvent may be any method known per seor a method in accordance therewith. For example, the organic solvent isevaporated at atmospheric pressure or under incrementally reducedpressure with stirring using a propeller stirrer, a magnetic stirrer ora ultrasonicating machine, or evaporated with adjusting the vacuum levelusing a rotary evaporator, or evaporated gradually using a dialyzingmembrane.

A microcapsule thus obtained is isolated using a centrifugation or afiltration, and any free forms of the physiologically active substanceor its salt, the hydroxynaphthoic acid or its salt, a vehicle, anemulsifier and the like deposited on the surface of the microcapsule arewashed off several times with distilled water, and then dispersed againin distilled water and lyophilized.

During a manufacturing process, an anti-aggregating agent may be addedin order to prevent the aggregation between particles. Suchanti-aggregating agent may for example be a water-soluble polysaccharidesuch as mannitol, lactose, glucose and starches (such as corn starch),an amino acid such as glycine, a protein such as fibrin and collagen.Among these, mannitol is employed preferably.

After a lyophilization, water and the organic solvent contained in themicrocapsule can be removed if necessary under reduced pressure bywarming while avoiding the fusion between the microcapsules.

Preferably, the warming is accomplished at a temperature which is higherslightly than the intermediate glass transition point of a lacticacid-glycolic acid polymer determined by a differential scanningcalorimeter with raising the temperature by 10 to 20° C. per minutes.The intermediate glass transition point of a lactic acid-glycolic acidpolymer to a temperature higher by about 30° C. than this temperature isthe range of the temperature at which the warming is accomplished morepreferably. Preferably, the warming is accomplished at a temperaturewithin the range from the intermediate glass transition point of alactic acid-glycolic acid polymer to a temperature which is higher thanthe intermediate glass transition point by 10° C., more preferably at atemperature within the range from the intermediate glass transitionpoint to a temperature which is higher than the intermediate glasstransition point by 5° C.

While the time period of the warming may vary depending on the amount ofa microcapsule and the like, it is usually about 12 hours to about 168hours, preferably about 24 hours to about 120 hours, especially about 48hours to about 96 hours after the temperature of the microcapsule itselfreached a certain temperature.

A method for warming is not limited particularly, as long as it enablesa uniform warming of a microcapsule bulk.

Such warming method may for example be a method for warming and dryingin a thermostat chamber, a fluidized tank, a mobile tank or a kiln, or amethod for warming and drying with a microwave. Among these methods, amethod for warming and drying in a thermostat chamber is preferred.

(ii) W/O/W Method (1)

First, a solution of a lactic acid-glycolic acid polymer or its salt inan organic solvent is preferred. The organic solvent and theconcentration of the lactic acid-glycolic acid polymer or its salt inthe organic solvent are similar to those described in theabove-mentioned (I)(I). When an organic solvent mixture is employed, theratio is also similar to that described in the above-mentioned (I)(i).

To a solution of the lactic acid-glycolic acid polymer or its salt in anorganic solvent thus obtained, a physiologically active substance or itssalt is added and dissolved or dispersed. Then the resultant organicsolvent solution (oil phase) containing a composition consisting of thephysiologically active substance or its salt and the lacticacid-glycolic acid polymer or its salt is combined with a solution of ahydroxynaphthoic acid or its salt [in the solvent such as water, anaqueous solvent such as an alcohol (e.g., methanol, ethanol), an aqueoussolution of pyridine, an aqueous solution of dimethylacetoamide]. Themixture is emulsified by a known method for example using a homogenizeror a ultrasonication to form a W/O emulsion.

Then the resultant W/O emulsion consisting of the physiologically activesubstance or its salt, the hydroxynaphthoic acid or its salt and thelactic acid-glycolic acid polymer or its salt is added to an aqueousphase to form a W(inner aqueous phase)/O(oil phase)/W(outer aqueousphase) emulsion, and then the solvent in the oil phase is evaporated toprepare a microcapsule. The volume of this outer aqueous phase isusually about 1 to about 10,000 times, more preferably about 5 to about5,000 times, especially about 10 to about 2,000 times the volume of theoil phase.

An emulsifier and an osmotic agent which may be added to an outeraqueous phase described above and the subsequent preparation are similarto those described in the above-mentioned (I) (i).

(iii) W/O/W Method (2)

First, a solution of a hydroxynaphthoic acid or its salt and a lacticacid-glycolic acid polymer or its salt in an organic solvent isprepared, and the resultant organic solvent solution is referred to asan oil phase. This production method is similar to that described in theabove-mentioned (I)(i). Alternatively, the hydroxynaphthoic acid or itssalt and the lactic acid-glycolic acid polymer or its salt may beformulated separately into organic solvent solutions, and thereafter theboth are mixed. While the concentration of the lactic acid-glycolic acidpolymer in an organic solvent solution may vary depending on themolecular weight of the lactic acid-glycolic acid polymer and the typeof the organic solvent, it is usually about 0.5 to about 70% by weight,more preferably about 1 to about 60% by weight, especially about 2 toabout 50% by weight, when using dichloromethane as an organic solvent.

Then a solution or a dispersion of a physiologically active substance orits salt [in the solvent such as water and a mixture of water and analcohol (e.g., methanol, ethanol)] is prepared. The concentration atwhich the physiologically active solution or its salt is added isusually 0.001 mg/ml to 10 g/ml, more preferably 0.1 mg/ml to 5 g/ml,particularly 10 mg/ml to 3 g/ml.

Known solubilizer and stabilizer may be added. For dissolving ordispersing the physiologically active substance and the additives,heating, shaking or stirring may be performed as long as the activity isnot lost, and the resultant aqueous solution is referred to as an inneraqueous phase.

The inner aqueous phase and the oil phase obtained as described above isemulsified by a known method for example using a homogenizer or aultrasonication to form a W/O emulsion.

The volume of the oil phase to be mixed is usually about 1 to about1,000 times, more preferably about 2 to about 100 times, especiallyabout 3 to about 10 times the volume of the inner water phase.

The resultant W/O emulsion is usually about 10 to about 10,000 cps,preferably about 100 to about 5,000 cps at about 12 to about 20° C.

Then the resultant W/O emulsion consisting of the physiologically activesubstance or its salt, the hydroxynaphthoic acid or its salt and thelactic acid-glycolic acid polymer or its salt is added to an aqueousphase to form a W(inner aqueous phase)/O(oil phase)/W(outer aqueousphase) emulsion, and then the solvent in the oil phase is evaporated ordiffused into the outer aqueous phase, whereby preparing a microcapsule.The volume of this outer aqueous phase is usually about 1 to about10,000 times, more preferably about 5 to about 50,000 times, especiallyabout 10 to about 2,000 times the volume of the oil phase. An emulsifierand an osmotic agent which may be added to an outer aqueous phasedescribed above and the subsequent preparation are similar to thosedescribed in the above-mentioned (I) (i).

(II) Phase Separation Method

When a microcapsule is prepared by this method, a coacervating agent isadded portionwise with stirring to a solution of a compositionconsisting of a pharmacologically active substance or its salt, ahydroxynaphthoic acid or its salt and a lactic acid-glycolic acidpolymer or its salt in an organic solvent described in the in-waterdrying method of the above-mentioned (I) to precipitate and solidify themicrocapsule. Such coacervating agent is about 0.01 to about 1,000times, preferably about 0.05 to about 500 times, particularly about 0.1to about 200 times the volume of the oil phase.

A coacervating agent is not particularly limited as long as it is apolymeric, mineral or vegetable compound miscible with an organicsolvent and it does not allow a complex of a physiologically activesubstance or its salt with a hydroxynaphthoic acid or its salt and alactic acid-glycolic acid polymer or its salt to be dissolved. Thoseexemplified typically are silicon oil, sesame oil, soybean oil, cornoil, cottonseed oil, coconut oil, linseed oil, mineral oils, n-hexane,n-heptane and the like. Any of these substance may be employed alone orin combination with each other.

The microcapsule thus obtained is isolated, washed repetitively forexample with heptane to make the composition consisting of thepharmacologically active substance or its salt, the hydroxynaphthoicacid or its salt and the lactic acid-glycolic acid polymer or its saltfree of the coacervating agent and other material, and then dried underreduced pressure. Alternatively, the washing is performed by the methodsimilar to that described in the in-water drying method in theabove-mentioned (I)(i), and then a lyophilizaiton followed by a dryingwith warming is performed.

(III) Spray-Drying Method

When a microcapsule is prepared by this method, a solution comprising apharmacologically active substance or its salt, a hydroxynaphthoic acidor its salt and a lactic acid-glycolic acid polymer or its salt in anorganic solvent described in the in-water drying method of theabove-mentioned (I) is sprayed via a nozzle into a drying chamber of aspray drier, whereby evaporating the organic solvent in amicroparticulate droplet within an extremely short period to prepare amicrocapsule. Such nozzle may for example be a dual-fluid nozzle, apressure nozzle, a rotating disc nozzle and the like. Subsequently, thewashing is performed if necessary by the method similar to thatdescribed in the in-water drying method in the above-mentioned (I) andthen a lyophilizaiton followed by a drying with warming is performed.

A microcapsule dosage form other than the microcapsule described abovecan be prepared by subjecting a solution comprising a pharmacologicallyactive substance or its salt, a hydroxynaphthoic acid or its salt and alactic acid-glycolic acid polymer or its salt in an organic solventdescribed in the in-water drying method of the above-mentionedmicrocapsule production method (I) for example to a rotary evaporator,where the organic solvent and water are evaporated into dryness withcontrolling the vacuum level, followed by a pulverization using a jetmill and the like, whereby obtaining a fine powder (also referred to asa microparticle).

Thereafter, the pulverized fine powder may be washed by the methodsimilar to that described in the in-water drying method in theabove-mentioned microcapsule production method (I) and then alyophilizaiton followed by a drying with warming is performed.

A microcapsule or a fine powder obtained here enables a medicamentrelease corresponding to the degradation rate of a lactic acid-glycolicacid polymer employed.

A sustained release composition according to the invention may be anydosage form such as a microsphere, a microcapsule, a fine powder(microparticle) and the like, it is preferably in the form of amicrocapsule.

A sustained release composition according to the invention can beformulated as it is or employed as a starting material to produce any ofvarious dosage forms, such as an intramuscular, subcutaneous or tissueinjection or implantation formulation, a nasal, rectal and intrauterinemucosal formulation, an oral formulation (e.g., solid dosage form suchas capsule including hard and soft capsules, granule and powder, liquidformulation such as syrup, emulsion and suspension) and the like.

When a sustained release composition according to the invention isformulated into an injection formulation, it is formulated into anaqueous suspension together with a dispersing agent (e.g., surfactantsuch as Tween 80 and HCO-60, polysaccharide such as sodium hyaluronate,carboxymethyl cellulose, sodium arginate and the like), a preservative(e.g., methylparaben, propylparaben), an isotonic agent (e.g., sodiumchloride, mannitol, sorbitol, glucose, proline), or dispersed togetherwith a vegetable oil such as sesame oil and corn oil to prepare an oilysuspension, whereby obtaining a practically utilizable sustained releaseinjection formulation.

The particle size of a sustained release composition when employed as asuspension injection formulation becomes acceptable when it allows thedispersing performance and the passage through the syringe needle to besatisfactory, and the mean particle size may for example be about 0.1 toabout 300 μm, preferably about 0.5 to about 150 μm, more preferableabout 1 to about 100 μm.

An aseptic formulation of a sustained release composition according tothe invention can be obtained for example by a method in which theentire manufacturing process is performed aseptically, a methodutilizing a sterilization with a gamma ray or a method in which apreservative is added, although there is no particular limitation.

Since a sustained release composition according to the invention has alow toxicity, it can be used as a safe pharmaceutical in a mammal (e.g.,human, cattle, swine, dog, cat, mouse, rat, rabbit).

While the dose of a sustained release composition according to theinvention may vary depending on the type and the content of aphysiologically active substance as a main ingredient, the dosage form,the duration of the release of the pharmacologically active substance,the target disease and the target animal, it may be an effective amountof the pharmacologically active substance. A single dose of apharmacologically active substance as a main ingredient, when thesustained release formulation is a 6-month formulation, is preferablyabout 0.01 mg to about 10 mg/kg body weight a day in an adult, morepreferably about 0.05 mg to about 5 mg/kg body weight.

The single dose of a sustained release composition is preferably about0.05 mg to about 50 mg/kg body weight in an adult, more preferably about0.1 mg to about 30 mg/kg body weight.

The frequency of the administration may be once in several weeks, once amonth or once in several months (e.g., 3, 4 or 6 months), depending onthe type and the content of a physiologically active substance as a mainingredient, the dosage form, the duration of the release of thepharmacologically active substance.

While a sustained release composition according to the invention can beused as a prophylactic and therapeutic agent against various diseasesdepending on the type of the pharmacologically active substancecontained therein, it, when containing an LH-RH derivative as apharmacologically active substance, can be used as a prophylactic andtherapeutic agent against a hormone-dependent disease, especially a sexhormone-dependent cancer (e.g., prostate cancer, uterine cancer, mammarycancer, pituitary cancer and the like), a sex hormone-dependent diseasesuch as prostate hyperplasia, endometriosis, hysteromyoma, precociouspuberty, dysmenorrhea, amenorrhea, premenstrual syndrome, multilocularovarian syndrome and the like, and useful as a contraceptive (or againstinfertility when utilizing a rebound effect after discontinuation). Itis also useful for treating a benign or malignant tumor which is not sexhormone-dependent but is LH-RH sensitive.

EXAMPLES

The present invention is further described with referring to thefollowing Examples and Experiments, which are not intended to restrictthe invention.

Example 1

A solution of 1.2 g of the acetate of5-oxo-Pro-His-Trp-Ser-Tyr-DLeu-Leu-Arg-Pro-NH—C₂H₅ (hereinafterabbreviated as Peptide A, Takeda Chemical Industries, Ltd.) dissolved in1.2 ml of distilled water was mixed with a solution of 4.62 g of aDL-lactic acid polymer (weight average molecular weight: 40,600, numberaverage molecular weight: 21,800, terminal carboxyl group level: 52.7μmol/g) and 0.18 g of 1-hydroxy-2-naphthoic acid dissolved in a solventmixture of 8.25 ml of dichloromethane and 0.45 ml of ethanol, andemulsified using a homogenizer to form a W/O emulsion. Then the W/Oemulsion was poured into 1200 ml of a 0.1% (w/w) aqueous solution of apolyvinyl alcohol (EG-40, Nippon Synthetic Chemical Industry Co., Ltd.)which had previously been kept at 15° C., and agitated using a turbinehomomixer at 7,000 rpm to form a W/O/W emulsion. This W/O/W emulsion wasstirred at room temperature for 3 hours to allow dichloromethane andethanol to be evaporated or diffused into the outer aqueous layer, andthen the oil phase was solidified, sieved through a 75 μm mesh-sizedsieve, centrifuged at 2000 rpm for 5 minutes (05PR-22, Hitachi, Ltd.) toprecipitate a microcapsule, which was then recovered. The microcapsulewas dispersed again in distilled water, centrifuged again, washed toremove free components and then recovered. To the recovered microcapsulewas added a small amount of distilled water to disperse again. 0.3 g ofmannitol was dissolved therein and then the mixture was lyophilized toobtain a powder. The % recovery as mass of the microcapsule was 46.91%,and the Peptide A content of the microcapsule was 18.7% while the1-hydroxy-2-naphthoic acid content was 2.57%.

Example 2

A solution of 1.2 g of the acetate of Peptide A dissolved in 1.2 ml ofdistilled water was mixed with a solution of 4.62 g of a DL-lactic acidpolymer (weight average molecular weight: 40,600, number averagemolecular weight: 21,800, terminal carboxyl group level: 52.7 μmol/g)and 0.18 g of 3-hyroxy-2-naphthoic acid dissolved in a solvent mixtureof 7.5 ml of dichloromethane and 0.45 ml of ethanol, and emulsifiedusing a homogenizer to form a W/O emulsion. Thereafter, the mixture wastreated similarly to EXAMPLE 1 to obtain a microcapsule powder. The %recovery as mass of the microcapsule was 53.18%, and the Peptide Acontent of the microcapsule was 17.58% while the 3-hydroxy-2-naphthoicacid content was 2.49%.

Experiment 1

About 45 mg of each microcapsule obtained in EXAMPLES 1 and 2 wasdispersed in 0.3 ml of a dispersion medium (0.15 mg of carboxymethylcellulose, 0.3 mg of polysorbate 80, 15 mg of mannitol dissolved indistilled water), and administered via a 22G injection needlesubcutaneously to a dorsal area of a 7-week old male SD rat. After apredetermined period, the rat was sacrificed and the microcapsuleremaining at the administration site was taken out, examined for thePeptide A content, which was divided by the initial content to obtain a% residue, which is shown in Table 1. TABLE 1 % Residue, Peptide AExample 1 Example 2 1 Day 92.9% 93.7% 2 Weeks 74.6% 78.8% 4 Weeks 56.0%58.0% 8 Weeks 31.6% 36.0% 12 Weeks 28.3% 32.3% 16 Weeks 24.5% 26.8% 20Weeks 17.8% 23.8% 26 Weeks 12.6% 15.6%

As evident from Table 1, both of the microcapsule of EXAMPLE 1containing 1-hydroxy-2-naphthoic acid and the microcapsule of EXAMPLE 2containing 3-hydroxy-2-naphthoic acid could contain the pharmaceuticallyactive substance at high concentrations, and exhibited an extremely highsuppressed effect on the initial excessive release of thephysiologically active substance. Any of these microcapsulesaccomplished a sustained release of the physiologically active substanceat a constant rate over an extremely prolonged period.

Example 3

A solution of 1.2 g of the acetate of Peptide A dissolved in 1.2 ml ofdistilled water was mixed with a solution of 4.62 g of a DL-lactic acidpolymer (weight average molecular weight: 32,000, number averagemolecular weight: 17,800, terminal carboxyl group level: 72.1 μmol/g)and 0.18 g of 3-hyroxy-2-naphthoic acid dissolved in a solvent mixtureof 7.5 ml of dichloromethane and 0.45 m of ethanol, and emulsified usinga homogenizer to form a W/O emulsion. Thereafter, the mixture wastreated similarly to EXAMPLE 1 to obtain a microcapsule powder. The %recovery as mass of the microcapsule was 51.2%, and the Peptide Acontent of the microcapsule was 18.05% while the 3-hydroxy-2-naphthoicacid content was 2.42%.

Experiment 2

About 250 mg of the microcapsule obtained in EXAMPLE 3 was dispersed in1.5 ml of a dispersion medium (0.75 mg of carboxymethyl cellulose, 1.5mg of polysorbate 80, 75 mg of mannitol dissolved in distilled water),and administered via a 22G injection needle intramuscularly to a rumparea of a beagle. One the other hand, about 125 mg of this microcapsulewas dispersed in 0.75 ml of a dispersion medium (0.375 mg ofcarboxymethyl cellulose, 0.75 mg of polysorbate 80, 37.5 mg of mannitoldissolved in distilled water), and administered via a 22G injectionneedle subcutaneously to a rump area of a beagle. After a predeterminedperiod, a blood was taken from a forearm vein and examined for the serumlevels of Peptide A and testosterone, which are shown in Table 2. TABLE2 Peptide A (ng/ml) Testosterone (ng/ml) Intramuscular administration 1Day 7.33 5.31 2 Weeks 0.76 0.46 4 Weeks 0.91 0.58 8 Weeks 3.65 0.25 orless 12 Weeks 1.56 0.25 or less 16 Weeks 1.14 0.25 or less 20 Weeks 0.590.25 or less 26 Weeks 0.53 0.25 or less 28 Weeks 0.48 0.25 or less 30Weeks 0.33 0.26 32 Weeks 0.37 0.79 34 Weeks 0.22 1.41 36 Weeks 0.14 0.94Subcutaneous administration 1 Day 17.61 2.79 2 Weeks 0.99 1.95 4 Weeks0.62 1.50 8 Weeks 0.76 0.68 12 Weeks 1.77 0.25 or less 16 Weeks 1.570.25 or less 20 Weeks 1.23 0.25 or less 26 Weeks 1.93 0.33 28 Weeks 0.351.59 30 Weeks 0.25 2.00

As evident from Table 2, the blood level of the physiologically activesubstance was maintained over a period as long as about 26 weeks, duringwhich the testosterone level as an index of the efficacy was kept at anormal level or lower, and then began to recover a normal level over aperiod of about 28 weeks to 34 weeks in response to the reduction in theblood level of the physiologically active substance. Even when ahydroxynaphthoic acid is contained in the formulation, thephysiologically active substance was present stably in the microcapsulefor a prolonged period without losing its activity whereby beingreleased sustainedly. It became also evident that the stable efficacywas exhibited regardless of the administration modes.

Example 4

A solution of 86.2 g of a DL-lactic acid polymer (weight averagemolecular weight: 28,300, number average molecular weight: 14,700,labeling method-based carboxyl group level: 69.2 μmol/g) dissolved in 67g of dichloromethane and 87.7 g of a solution obtained by dissolving 9 gof 3-hydroxy-2-naphthoic acid in 210 g of dichloromethane and 16.2 g ofethanol were mixed and adjusted at 28.8° C. 219.2 g of this organicsolvent solution was weighed and mixed with an aqueous solution of 20.4g of the acetate of Peptide A dissolved in 18.8 g of distilled waterkept at 54.8° C., and the mixture was stirred for 5 minutes to emulsifyonly crudely, and then emulsified using a homogenizer at 10,000 rpm for5 minutes to form a W/O emulsion. Then this W/O emulsion was cooled to12.7° C. and the poured over a period of 5 minutes and 11 seconds into20 L of a 0.1% (w/w) aqueous solution of a polyvinyl alcohol (EG-40,NIPPON SYNTHETIC CHEMICAL INDUSTRY CO., LTD.) which had previously beenkept at 12.7° C., and agitated using HOMOMIC LINE FLOW (TOKUSHUKIKAI) at9,000 rpm to form a W/O/W emulsion. This W/O/W emulsion was adjusted at15° C. for 30 minutes, and then stirred without adjusting thetemperature for 2 hours and 30 minutes to allow dichloromethane andethanol to be evaporated or diffused into the outer aqueous layer, andthen the oil phase was solidified, sieved through a 75 μm mesh-sizedsieve, centrifuged at 2000 rpm continuously (H-600S, KOKUSANENSHINKI) toprecipitate a microcapsule, which was then recovered. The recoveredmicrocapsule was dispersed again in a small amount of distilled water,and sieved through a 90 μm mesh-sized sieve. 12.3 g of mannitol wasdissolved therein and then the mixture was lyophilized to obtain apowder. The yield as mass of the microcapsule was 84.4 g, whichcorresponded to the % recovery of 75.7%, and the Peptide A content was17.8% while the 3-hydroxy-2-naphthoic acid content was 2.5%.

Example 5

A solution of 107.8 g of a DL-lactic acid polymer (weight averagemolecular weight:27,700, number average molecular weight:15,700,labeling method-based carboxyl group level:69.8 μmol/g) dissolved in83.9 g of dichloromethane and 110.2 g of a solution obtained bydissolving 7.5 g of 1-hydroxy-2-naphthoic acid in 175.8 g ofdichloromethane and 13.5 g of ethanol were mixed and adjusted at 28.2°C. 274.2 g of this organic solvent solution was weighed and mixed withan aqueous solution of 25.6 g of the acetate of Peptide A dissolved in23.52 g of distilled water kept at 52.4° C., and the mixture was stirredfor 5 minutes to emulsify only crudely, and then emulsified using ahomogenizer at 10,080 rpm for 5 minutes to form a W/O emulsion. Thenthis W/O emulsion was cooled to 12.5° C. and the poured over a period of3 minutes and 42 seconds into 25 L of a 0.1% (w/w) aqueous solution of apolyvinyl alcohol (EG-40, NIPPON SYNTHETIC CHEMICAL INDUSTRY CO., LTD.)which had previously been kept at 13.1° C., and agitated using HOMOMICLINE FLOW (TOKUSHUKIKAI) at 7,000 rpm to form a W/O/W emulsion. ThisW/O/W emulsion was adjusted at 15° C. for 30 minutes, and then stirredwithout adjusting the temperature for 2 hours and 30 minutes to allowdichloromethane and ethanol to be evaporated or diffused into the outeraqueous layer, and then the oil phase was solidified, sieved through a75 μm mesh-sized sieve, centrifuged at 2000 rpm continuously (H-600S,KOKUSANENSHINKI) to precipitate a microcapsule, which was thenrecovered. The recovered microcapsule was dispersed again in a smallamount of distilled water, and sieved through a 90 μm mesh-sized sieve.15.4 g of mannitol was dissolved therein and then the mixture waslyophilized to obtain a powder. The yield as mass of the microcapsulewas 105.7 g, which corresponded to the % recovery of 75.8%, and thePeptide A content was 17.8% while the 1-hydroxy-2-naphthoic acid contentwas 2.8%.

Example 6

A solution of 107.6 g of a DL-lactic acid polymer (weight averagemolecular weight: 30,800, number average molecular weight: 13,900,labeling method-based carboxyl group level: 66.3 μmol/g) dissolved in83.3 g of dichloromethane and 109.7 g of a solution obtained bydissolving 7.5 g of 1-hydroxy-2-naphthoic acid in 175 g ofdichloromethane and 13.5 g of ethanol were mixed and adjusted at 28.7°C. 274.3 g of this organic solvent solution was weighed and mixed withan aqueous solution of 24.89 g of the acetate of Peptide A dissolved in23.49 g of distilled water kept at 51.2° C., and the mixture was stirredfor 5 minutes to emulsify only crudely, and then emulsified using ahomogenizer at 10,070 rpm for 5 minutes to form a W/O emulsion. Thenthis W/O emulsion was cooled to 12.8° C. and the poured over a period of4 minutes and 13 seconds into 25 L of a 0.1% (w/w) aqueous solution of apolyvinyl alcohol (EG-40, NIPPON SYNTHETIC CHEMICAL INDUSTRY CO., LTD.)which had previously been kept at 13.3° C., and agitated using HOMOMICLINE FLOW (TOKUSHUKIKAI) at 7,000 rpm to form a W/O/W emulsion. ThisW/O/W emulsion was adjusted at 15° C. for 30 minutes, and then stirredwithout adjusting the temperature for 2 hours and 30 minutes to allowdichloromethane and ethanol to be evaporated or diffused into the outeraqueous layer, and then the oil phase was solidified, sieved through a75 μm mesh-sized sieve, centrifuged at 2000 rpm continuously (H-600S,KOKUSANENSHINKI) to precipitate a microcapsule, which was thenrecovered. The recovered microcapsule was dispersed again in a smallamount of distilled water, and sieved through a 90 μm mesh-sized sieve.15.4 g of mannitol was dissolved therein and then the mixture waslyophilized to obtain a powder. The yield as mass of the microcapsulewas 101.9 g, which corresponded to the % recovery of 73.1%, and thePeptide A content was 17.3% while the 1-hydroxy-2-naphthoic acid contentwas 2.9%.

Experiment 3

About 45 mg of each microcapsule obtained in EXAMPLES 5 and 6 wasdispersed in 0.3 ml of a dispersion medium (0.15 mg of carboxymethylcellulose, 0.3 mg of polysorbate 80, 15 mg of mannitol dissolved indistilled water), and administered via a 22G injection needlesubcutaneously to a dorsal area of a 7-week old male SD rat. After apredetermined period, the rat was sacrificed and the microcapsuleremaining at the administration site was taken out, examined for thePeptide A content, which was divided by the initial content to obtain a% residue, which is shown in Table 3. TABLE 3 % Residue, Peptide AExample 5 Example 6 1 Day 87.0% 90.5% 1 Week 80.0% 83.2% 2 Weeks 72.3%73.5% 4 Weeks 57.6% 58.0% 8 Weeks 48.2% 46.7% 12 Weeks 34.5% 32.8% 16Weeks 23.1% 22.0% 20 Weeks 14.7% 13.4% 26 Weeks 6.1% 3.3%

As evident from Table 3, both of the microcapsules of EXAMPLES 5 and 6containing 1-hydroxy-2-naphthoic acid, which differed in the molecularweight of the lactic acid polymer as a base, could contain thepharmaceutically active substance at high concentration even when eachwas produced on the scale of about 125 g, and exhibited an extremelyhigh suppressed effect on the initial excessive release of thephysiologically active substance. Any of these microcapsulesaccomplished a sustained release of the physiologically active substanceat a constant rate over an extremely prolonged period.

INDUSTRIAL APPLICABILITY

An inventive sustained release composition contains a pharmacologicallyactive substance at a high concentration and suppresses the initialexcessive release of this substance, and maintains a stable releasingrate for a prolonged period (preferably about 6 months or longer).

1. A sustained release composition comprising a pharmacologically activesubstance or its salt, a hydroxynaphthoic acid or its salt and a lacticacid-glycolic acid polymer or its salt, wherein the product of theweight average molecular weight of said lactic acid-glycolic acidpolymer by the amount (μmol) of the terminal carboxyl group per unitmass (g) of said lactic acid-glycolic acid polymer is 1,200,000 to3,000,000 (inclusive).
 2. The sustained release composition according toclaim 1, wherein the pharmacologically active substance is aphysiologically active peptide.
 3. The sustained release compositionaccording to claim 1, wherein the pharmacologically active substance isan LH-RH derivative.
 4. The sustained release composition according toclaim 1, wherein the hydroxynaphthoic acid is 1-hydroxy-2-naphthoicacid.
 5. The sustained release composition according to claim 1, whereinthe % molar ratio between lactic acid and glycolic acid is 100/0 to40/60.
 6. The sustained release composition according to claim 1,wherein the % molar ratio between lactic acid and glycolic acid is100/0.
 7. The sustained release composition according to claim 1,wherein the weight average molecular weight of the polymer is about3,000 to about 100,000.
 8. The sustained release composition accordingto claim 7, wherein the weight average molecular weight is about 20,000to about 50,000.
 9. The sustained release composition according to claim3, wherein the LH-RH derivative is a peptide represented by Formula:5-oxo-Pro-His-Trp-Ser-Tyr-Y-Leu-Arg-Pro-Z wherein Y denotes DLeu, DAla,DTrp, DSer(tBu), D2NaI or DHis(ImBzl), and Z denotes NH—C₂H₅ or Gly-NH₂.10. The sustained release composition according to claim 1, wherein theamount (μmol) of the terminal carboxyl group of the polymer is 50 to 90μmol per unit mass (g) of the polymer.
 11. The sustained releasecomposition according to claim 3, wherein the molar ratio between thehydroxynaphthoic acid or its salt and the LH-RH derivative or its saltis 3:4 to 4:3.
 12. The sustained release composition according to claim3 which contains the LH-RH derivative or its salt in an amount of 12% byweight to 24% by weight based on the sustained release composition. 13.The sustained release composition according to claim 1, wherein thephysiologically active substance or its salt is a slightly water-solubleor water-soluble substance.
 14. The sustained release compositionaccording to claim 1 which is a formulation for injection.
 15. Amedicament comprising a sustained release composition according toclaim
 1. 16. A prophylactic or therapeutic agent against prostatecancer, prostate hyperplasia, endometriosis, hysteromyoma, metrofibroma,precocious puberty, dysmenorrhea or mammary cancer or an contraceptivecontaining a sustained release composition according to claim
 3. 17. Thesustained release composition according to claim 1, wherein thepharmacologically active substance or its salt is released over a periodof at least 6 months or longer.
 18. A sustained release compositioncomprising a pharmacologically active substance or its salt,1-hydroxy-2-naphthoic acid or its salt and a biodegradable polymer orits salt.